The present invention relates to fiber optic data transmission systems and more particularly to a secure fiber optic data transmission system.
The present invention is an arrangement to provide protection against external physical tampering with an optical fiber carrying data modulated on the light beam propagated in the optical fiber. The arrangement prevents tapping or otherwise obtaining classified or otherwise sensitive data propagating in the fiber. In the past, other techniques have been developed for securing transmission in an optical fiber such as the use of special concentric core fibers or the use of special couplers for modal multiplexing of various signals on a signal optical fiber. More conventional techniques for providing physical security of data transmission includes encryption or physical protection in one of many forms such as:
(a) Physical hardening, such as, reinforced concrete ducts or ferrous metal welded pipes; PA1 (b) Physical hazards, such as, toxic gases, high voltage, explosives, or trained dogs; and PA1 (c) Monitors and alarms, such as, pressurized conduits, electrical capacitance variation, TV cameras, and guard surveillance.
All of the above mentioned devices share the shortcomings of high costs and high complexities. In addition, they are often rather inconvenient and/or unattractive.